本研究旨在探討大聯盟於2012年與2022年外卡改制對季末觀眾人數的影響。隨著大聯盟近年來票房逐年下滑，聯盟方面相應地透過創新規則或改變賽制來解決這一問題。在2012年與2022年，聯盟分別將各聯盟的外卡席次增加至2席及3席，季後賽的規模因此由最初的8支球隊擴展至10支及12支。本文基於過去文獻的假設，認為季後賽的改制能提升季後賽不確定性，並採用雙重差分法（difference-in-differences, DID）建立因果推斷模型進行分析。本研究收集了大聯盟30支球隊在2002年至2023年間的資料，其中2002年至2011年及2012年至2019年為2012年外卡政策實施前後的樣本區間，而2013年至2019年及2022年至2023年則為2022年政策實施前後的樣本區間。季末則定義為九月份之後的比賽。在DID模型的設計上，以勝差（GB）小於等於8作為實驗組的定義標準，假設此類樣本為受政策影響的族群；反之，勝差大於8則設為對照組。研究結果顯示，2012年外卡改制不僅未能達成預期的政策效果，反而對票房造成負成長；相對而言，2022年外卡改制則顯著提升了季末票房，使球場的滿座率平均提升了6%。

The purpose of this study is to examine the impact of the Wild Card reform on attendance in 2012 and 2022. As attendance has been declining in recent years, the league has tried to solve the problem by renovating rules and making changes to the competition system accordingly. MLB expanded the wild card spots for each league to two and three spots in the 2012 and 2022 seasons, and the size of the playoffs has therefore been expanded from 8 teams to 10 and 12 teams. Based on the assumption from previous studies, which suggests that expanding the postseason spots can increase the playoff uncertainty, this paper uses the difference-in-differences (DID) method to build a causal inference model and collects MLB all 30 teams' game data from 2002 to 2023. 2002-2011 and 2012-2019 are the pre- and post-reform periods of policy 2012, while 2013-2019 and 2022-2023 are the pre- and post-reform periods of policy 2022. Under the framework of DID, we define the teams with a games behind (GB) of no greater than eight as the treatment group, which are the samples affected by the Wild Card reform. Otherwise, we classified them as the control group. Our empirical results show that the Wild Card expansion in 2012 not only failed to achieve the expected policy effects but also led to a decline in attendance. In contrast, the policy effects of the 2022 Wild Card reform have a positive impact on fan demand, which causes attendance to increase by 6 percentage points on average.

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